An electrical network can have multiple energy sources that can be used to provide multiple loads connected to the electrical network with electric power. In this arrangement, it is additionally possible for the electrical network to be divided into multiple subnetworks that each have different associated energy sources and loads. The different subnetworks can have different voltages that can be used to operate the subnetworks, these different voltages having different amplitudes and/or different maximum values. Two subnetworks connected to one another in this case and having different voltages are connected to one another via a voltage transformer, for example a DC voltage transformer or an AC voltage transformer.
The document U.S. Pat. No. 5,093,583 A, which is incorporated by reference herein, discloses an electrical system for a motor vehicle that comprises a low voltage network and a high voltage network. In this case, a generator produces a low voltage that feeds the low voltage network and a transformer of the motor vehicle. This transformer is configured to convert the low voltage into a high voltage that can also be used to operate loads in the high voltage network in parallel with loads in the low voltage network.
A method for supplying an electric motor with an AC current is described in the document US 2010 0 140 003 A1, which is incorporated by reference herein. In this case, depending on the requirement of the electric motor, the latter is provided with a voltage by means of at least one pulse width modulation, a selection being made between multiple types, for example three types, of a respective pulse width modulation to be used.
The document US 2013 0 106 365 A1, which is incorporated by reference herein, discloses the practice of charging an energy store of an electric motor vehicle via an external energy source. In this case, it is possible to charge the energy store of the motor vehicle using the external energy source in DC isolated or direct fashion.
A fuel cell system by means of which electrical loads are able to be supplied with electric power is described in the document US 2014 0 152 089 A1, which is incorporated by reference herein. In this case, a respective fuel cell and a respective electrical load have an inverter arranged between them that is configured to produce a polyphase high voltage needed by the respective load, undesirable noise being avoided by selecting a difference for phases of the high voltages.
The document US 2014 0 225 432 A1, which is incorporated by reference herein, discloses a current transformer that comprises three coils and is configured for exchanging electric power between various voltage sources and voltage networks of an electric motor vehicle.